Matrix converters (or cycloconverters) may be used in electric and/or hybrid vehicles to accommodate delivery of relatively high power over a relatively wide range of operating voltages, while at the same time achieving galvanic isolation, relatively high power factors, low harmonic distortion, relatively high power density and low cost. Matrix converters may be used to deliver energy from an alternating current (AC) energy source, such as the single-phase grid electricity common in most residential and commercial buildings, to a direct current (DC) energy storage element, such as a rechargeable battery, in the vehicle.
In practice, it may be desirable to shutdown or otherwise deactivate the matrix converter, for example, to stop delivering charging power to a vehicle battery or to reduce switching losses. In some matrix converter systems, one or more reactive components (e.g., inductors and/or capacitors) are present between the AC energy source and the matrix converter. When the matrix converter is deactivated, the current flowing to/from the matrix converter is interrupted or otherwise stopped. However, abruptly stopping the current to/from a reactive component(s) may result in a potentially damaging voltage spike across components of the matrix converter caused by the potential energy stored by the reactive component(s). For example, abruptly stopping the current flowing through an inductor may result in a transient voltage spike that exceeds the breakdown voltage of a semiconductor device.
Many prior art systems utilize one or more snubbers to prevent or otherwise mitigate harm that could otherwise result from voltage spikes across components of the matrix converter. Snubbers are additional lossy components that reduce the overall efficiency of operation. Accordingly, it is desirable that any potential energy stored by the reactive component(s) be discharged in a manner that protects components of the matrix converter upon shutdown without requiring the use of snubbers or other lossy components.